Updated project metadata. During the last decade, skeletal muscle-secreted proteins have been identified with important roles in intercellular communications. To investigate whether muscle-derived exosomes participate in this molecular dialog, we determined and compared the protein contents of the exosome-like vesicles (ELVs) released from C2C12 murine myoblasts during proliferation (ELV-MB), and after differentiation into myotubes (ELV-MT). Using a proteomic approach combined with electron microscopy, western-blot and bioinformatic analyses, we compared the protein repertoires within ELV-MB and ELV-MT. RAW files were processed using MaxQuant [28] version 1.3.0.3. Spectra were searched against the Uniprot database (August 2012 version, Mus musculus taxonomy 10090, 86644 sequences, Bos taurus taxonomy 9913, 34280 sequences and Equus caballus taxonomy 9796, 24299 sequences) and the frequently observed contaminants database (notably containing protein sequences from serum proteins) embedded in MaxQuant. Trypsin was chosen as the enzyme and 2 missed cleavages were allowed. Precursor mass error tolerances were set respectively at 20 ppm and 6 ppm for first and main searches. Fragment mass error tolerance was set to 0.5 Da. Peptide modifications allowed during the search were: trioxidation (C, fixed), acetyl (N-ter, variable), dioxidation (M, variable), oxidation (M, variable) and deamidation (NQ, variable). Minimum peptide length was set to 7 amino acids. Minimum number of peptides, razor+unique peptides and unique peptides were set respectively to 2, 2 and1. Maximum false discovery rates - calculated by employing a reverse database strategy - were set to 0.01 at peptide and protein levels.